1. Field of the Invention
The present invention relates to a polling method, and more particularly, to a polling method compliant to Bluetooth protocol for increasing transfer efficiency.
2. Description of the Prior Art
In Bluetooth protocol, when a master has to continuously request slaves to transfer data, the master can poll the slaves. For example, the master is a game console, and the slaves are the joysticks corresponding to the game console. In a multiplayer game, each joystick has to continuously transfer vast control signals sent by the users through the joysticks to the game console, so that the game console can accordingly control the characters representing the users in the game. Thus, the game console (the master) polls each joystick (slave) for obtaining the control signals at the time.
Please refer to FIG. 1. FIG. 1 is a diagram illustrating a conventional polling method. In FIG. 1, the period length of the time slots TS0˜TS11 are all equal to a cycle T (for example, 625 μs). In the upper part of FIG. 1, the master MA polls the slaves SL1 and SL2, wherein the master MA and the slaves SL1, and SL2 belong to the same Bluetooth piconet, and the master MA assigns an address ADDR1 to the slave SL1, and an address ADDR2 to the slave SL2, respectively. First, the master MA sends a polling packet PP1 in the polling time slot TS0, wherein the polling packet PP1 has the address ADDR1. Hence, when the slave SL1 receives the polling packet PP1, the slave SL1 can determine that the master MA requests the slave SL1 to respond according to the address ADDR1 included in the polling packet PP1. Meanwhile, the slave SL1 sends a responding packet RP1 (corresponding to the polling packet PP1) for transferring data to the master MA in a responding time slot TS1 adjacent to the polling time slot TS0. Next, the master MA sends a polling packet PP2 in the polling time slot TS2, wherein the polling packet PP2 has the address ADDR2. Similarly, the slave SL2 can determine that the master MA requests the slave SL2 to respond according to the address ADDR2 included in the polling packet PP2. Hence, the slave SL2 sends a responding packet RP2 (corresponding to the polling packet PP2) for transferring data to the master MA in a responding time slot TS3 adjacent to the polling time slot TS2. Consequently, the master MA can poll the slaves SL1 and SL2 for one time every four time slots. In the lower part of FIG. 1, the master MA polls the slaves SL1, SL2, and SL3, wherein the master MA and the slaves SL1, SL2, and SL3 belong to the same Bluetooth piconet, and the master MA assigns the addresses ADDR1, ADDR2, and ADDR3 to the slaves SL1, SL2, and SL3, respectively. The method of the master MA polling the slaves SL1, SL2, and SL3 is similar to the method of the master MA polling the slaves SL1 and SL2, as shown in the upper part of FIG. 1, and thus the related explanation will not be repeated again for brevity. As shown in the lower part of FIG. 1, the master MA can poll the slaves SL1, SL2, and SL3 for one time every six time slots.
According to the illustration of FIG. 1, it can be known that when a master is to poll M slaves, the master has to send M polling packets in M polling time slots, respectively, and the period length of the master polling M slaves for one time is equal to (2×M) time slots, wherein M represents a positive integer. As a result, when the number of the slaves increases (M becomes larger), the number of the polling packets sent by the master increases. In this way, the transfer efficiency is reduced, causing a great inconvenience.